Building Your Own Drivers? 34
students asks: "I want to cheaply demonstrate how speaker 'drivers' (the part that makes the noise, not software...also known as a cone) work, not to produce ideal sound. Some quick research has made it clear that it's easy to find directions on how to build a fancy speaker box, but not much on how to make a driver. Unfortunately, I can't use Sake. I also can't get the thin wood. Does anyone know how to build a driver out of home materials?"
EASY! (Score:3, Interesting)
That's a simple speaker and how many of the really cheap ear-phones work.
Let me tell you how I did it... (Score:3, Interesting)
I started out with a largish cardboard box, and traced a large circle on the front, and cut it out with a steak knife. I then made a paper flattened "cone" out of construction paper (a little larger than the hole), made a bunch of radial slits along the edge, then bent, formed, and glued this to the hole. At the apex of the cone (inside the box), I had glued a piece of toilet paper tubing upon which I had wound a mess of wire I had gotten from the windings on a motor armature (as I remember, I didn't do a very neat job of winding it). On the backside of the cardboard, underneath the tube, I mounted (with a bunch of duct tape) a piece of speaker magnet I had (for some reason, when I was a kid, it was far easier to get speaker magnets than whole, large speakers - but I digress). I hooked the wires from the coil up to a radio - and it worked!
Not much bass, but it was definitely a working "loudspeaker". You could probably take this same technique and apply it to build a much better speaker, perhaps even something to act as a demonstration model. With a little thought, you could even put together a bunch of "speaker kits", if you are teaching a class or something...
Alright, (Score:2, Interesting)
Now, to get a decent shape, suspension, and spider for your speaker, you may want to make your own paper and mold it onto the shapes.
Start with Play-Doh® or something similar. Shape out the cone and suspension nicely. Then, make a plaster (flour, if need be) cast of it. Then cast that, and seal the result. Now you have a mold to form your cone. Do the same with the design for the spider. The great thing about this process is you don't have slits or glue or such to damage your sound.
Now, make paper soup. It involves blending newspaper... Links should be plentiful on Google. Look for: make paper newspaper blender. Coating and drying is another issue. A fabric-covered sponge (so it doesn't grab the paper) might do the trick. Granted, I'm making this up as I go along. I will conservatively estimate 4 tries for a decent result, given attention to detail.
Once dry, you have the difficult components of your speaker, and they should produce better sound than most throw-together items.
Of course, this may cost more in time and money than you really want.
Better lesson - use old speaker (Score:5, Interesting)
Next I take a cheap sine wave generator (you can get kits that cost $10) and set the frequency to maybe 5Hz (you can find cheap multi-meters that measure Hz). The point here isn't to listen (you can't) but to see the cone moving in and out. This helps the student see that the signal going to a speaker is alternating current (AC) and it quickly moves the speaker back and forth. Higher frequencies move the cone so little or so fast that it's difficult for the student to understand what's happening. So starting with a low frequency and then turning up the frequency helps the student see exactly why the speaker is making sound. The bigger the speaker the better this demonstration works. I usually had 15" drivers to mess with and you can really see the cone move at frequencies below 20.
Have fun.